Discussion of 'Cross Correlations of Modal Responses of Tall Buildings in Wind-Induced Lateral-Torsional Motion' by M. F. Huang, C. M. Chan, K. C. S. Kwok, and P. A. Hitchcock
| Autor: | Xinzhong Chen, Ahsan Kareem |
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| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | Journal of Engineering Mechanics. 137:151-154 |
| ISSN: | 1943-7889 0733-9399 |
| DOI: | 10.1061/(asce)em.1943-7889.0000164 |
| Popis: | The paper presented a slightly enhanced closed-form expression for estimating the modal correlation coefficients of wind-excited structures needed for complete quadratic combination CQC of response in various modes by extending the expression proposed in Chen and Kareem 2005 . The modal correlation coefficient between two adjacent modes, needed for the implementation of the CQC scheme, is often estimated using the closed-form formulation given in Der Kiureghian 1980 for the analysis of wind load effects on buildings and other structures, e.g., Xie et al. 2003 . Chen and Kareem 2005 emphasized that this formulation is valid only when the generalized forces are fully correlated, for example, in the case of buildings with an earthquake input excitation. The modal correlation coefficient depends not only on the modal frequencies and damping ratios but also on the correlation/coherence of the generalized forces. A utilization of the formulation in Der Kiureghian 1980 , primarily intended for earthquake load effects, will overestimate the modal correlation associated with multiple excitations of partially correlated loads, e.g., wind loads. Following the derivation given in Chen and Kareem 2005 , in which the cospectrum, i.e., the real part of the cross power spectral density XPSD function, of the generalized wind forces has been included, the authors have proposed including the quad-spectrum, i.e., the imaginary part, in an effort to further improve the estimate of modal response correlation. When comparing the original work by Chen and Kareem to the study by Huang et al., one will find that the latter essentially echoes and reinforces the viewpoints expressed in the former concerning the need for a modified CQC scheme and its implications in the case of wind-excited structures. Unfortunately, it does so with only a marginal and obscurely placed attribution to this original work, which may leave a casual reader with the impression that Huang et al. were indeed the first to unveil this issue. Using a 60-story building as an example, the paper compared three different schemes for calculating the modal correlation coefficients and their influence on the predictions of building accelerations using the CQC rule. These schemes include: 1 TCQC, in which the generalized forces are assumed to be fully coherent conventional approach used in analysis prior to Chen and Ka |
| Databáze: | OpenAIRE |
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